The hardest part of investing can sometimes be getting out of your own way. Too often, we let emotions guide our investing strategies, with disastrous results. A new study reveals the most common mistakes: We've summed up the popular pitfalls so you can avoid them.

In 2008, R.P. McCabe saw a $1 million investment in real estate disappear, not due to the recession, but a Ponzi scheme that robbed around 700 investors of $100 million. First he got mad. Then he got depressed. Next, he got curious. And then he wrote a novel based on the experiences of his fellow victims: "Betrayed."

After all the times people have been duped by Ponzi schemes and Nigerian scams, people still fall for similar cons. But in the case of the .44 Magnum Leveraged Financing Program, some investors recently found a way to lose their money with a real bang.

A top executive in the now-defunct empire of disgraced Texas financier R. Allen Stanford was sentenced to three years in prison Thursday for her role in helping the once jet-setting businessman bilk investors out of more than $7 billion in one of the biggest Ponzi schemes in U.S. history.

Here's a disturbing fact about Social Security you may not have heard about: For an increasing number of new retirees, the amount that Social Security will pay out in benefits will end up being less than the payroll taxes they paid in.